In 3 to 4-quart slow cooker, combine all ingredients except penne and pesto; mix well.
Cover; cook on Low setting for 8 to 9 hours.
About 20 minutes before serving, stir penne into soup. Increase heat setting to High; cover and cook an additional 15 to 20 minutes or until penne is tender.
To serve, top individual servings with 2 teaspoons pesto.